Turnips, 43 Borough Market, London SE1 9AH (020 7357 8356). Small plates (Wednesday-Saturday) £5-£9, wines from £33, tasting menu (Thursday-Saturday) £65

Fred Foster always dreamed of having a restaurant. He’d supplied fruit and veg to some of the grandest places in London: to the Dorchester and Le Gavroche, and to the great Nico Ladenis in his pomp. It was the logical step. In the end it took a pandemic to make it a reality. “If it hadn’t been for lockdown, we wouldn’t have had a chance to work alongside so many chefs,” Fred told me, when I spoke to him a few days after eating at his pop-up, carved out of the enclosure which, during the day, houses his produce company, Turnips. “That’s how this happened.”

Turnips is a brazen, shameless display of what plants can do given the right encouragement. When Borough Market is at full, gustatory throttle it’s one of those places you go to gawp: at tumbles of wild mushrooms, and vast arrays of melons piled high; at fat, scarlet-blushed radishes, and tangled thickets of green herbs. Turnips, which started in Pimlico, was one of the original traders to move to Borough more than three decades ago, long before its rebirth as a duck confit stuffed, pork pie mongering, gruyère and truffle peddling, oyster crusted retail food destination in the late 90s.

It remained a fixed point as the space went through ever more polished renovations. Few things have stayed the same at Borough over the years. There’s the chorizo roll from Brindisa, more cultural icon than mere food item. And then there’s Turnips. (Side note: I have no patience for those who now sneer at Borough as some tawdry tourist spot. If the market was elsewhere in Europe, the very same self-appointed food grandees who dismiss it would be crawling on their greasy hands and knees to be there and would boast about doing so.)

From early in lockdown, Turnips was sending fruit and veg boxes to vulnerable groups in need, and cooks from some of the restaurants they usually supplied came to help. Among them was Tomas Lidakevicius, one-time executive chef at Jason Atherton’s City Social. “It was while working side by side that we came up with the plan,” Fred says. Or to be exact, two plans. Across from the main Turnips enclosure, tables and chairs have been set out. There’s a temporary open kitchen from which Lidakevicius serves a five-course tasting menu for £65 a head, designed to show off the produce at hand to its best advantage, with flourish and bravado. In the current economic circumstances that strikes me as a brave move.

Certainly, I was more interested in the second part of the operation. At 5.30pm every Wednesday to Saturday, Turnips closes and most of the produce is shifted out, save for an escarpment of squash here or a hillside of apples there. Black drapes cover the emptied stands and high-top tables are brought in. Turnips becomes a small-plates restaurant, serving cocktails and a short menu of dishes priced at between £5 and £9. A few baby turnips are involved. They arrive alongside slices of crisp radish and batons of pepper, among other things, to be dragged through a rough-hewn, punchy hummus, the surface dusted with rust-coloured spice.

To start there are long rectangles of bread which have been deep-fried to a shattering, come-hither golden, alongside an airy, whipped and still warm sauce of cheddar and garlic. Bruschetta are piled with a sea-green pesto made with cavolo nero, with just the edge of the leaf’s bitterness, then topped with the sweetest of chopped tomatoes. A dinky, round Provençal courgette arrives, browned and burnished until just beginning to sag. It has been sliced open, scooped out and filled with a mess of tomatoes, basil and breadcrumbs.

A thick, cumin-boosted purée of sweet potato and lentils is formed into deep-fried croquettas. They arrive dotted with wasabi mayo, some of which hold the tiniest fronds of a purple leaf. It looks very pretty, but more importantly those croquettas are extravagantly moreish. And, as it happens, Moorish. I am taken by small, taut-skinned fish balls because they remind me, in semi-Proustian fashion, of the fish balls sold by the Jewish deli where I was tolerated for a short-lived Saturday job when I was a kid. They are dense and have a pronounced and unashamed fishiness. It’s mediated by the rowdy, spiced Sicilian pepper sauce underneath.

Two dishes miss the mark. A sizeable chunk of pork belly, the only meat on the menu, needs a longer, more complex trip through the oven so it slumps rather than puts up a struggle against my fork, though the sticky peach compôte on top is appreciated. Likewise, sweet-sour caramelised cauliflower is just a little wan and uninteresting. Then again, the brigade in the kitchen numbers just one. He’s a young Scot with killer hair, also formerly from City Social, called Scott Murray, who works minor miracles with the most minimal of kit.

The one dessert is a pleasing mess of chia seeds, in a coconut milk pudding with diced and puréed mango. It is, like so much here, a reminder of the lovely things they sell at Turnips. I also ask nicely, and get the dessert from Lidakevicius’s tasting menu brought over. It’s one of those extremely pleasing compendiums of chocolate and cherries in multiple textures, each dollop placed just so.

The waiters are recruits from the grander of London’s still-sleeping restaurants, who are clearly delighted to be working. Even so, there is a Summer Stock feel, of the show being put on, right here, in the pigeon-roosted, soot-caked barn. That rackety element is best represented by the short and unrewarding wine list. They can do better than £33 for the cheapest white, a sturdy but unremarkable Kiwi sauvignon blanc.

But there is also something lovely about what they’re doing here. Borough Market can’t quite be itself at the moment. Nowhere can. They have created a one-way system through the stands, and there are many blank corners. But this feels like a clever response to these challenging circumstances. Eating outside is desirable right now. There is space to distance the tables. And then there’s the Turnips stock, sales of which must be down right now. How better to deal with that than by serving some of it? And so, finally, Fred has his restaurant. It will run at least until the end of September.

News bites

Among the food businesses reopening at the moment is the Leeds Cookery School, a social enterprise which donates all its profits to Zest, a charity supporting vulnerable people and those dealing with poverty across the city. They have just launched a course in Greek cookery, perfect for anyone missing their getaway this year, and in November they’ll be running a class in the food of Vietnam (leedscookeryschool.org.uk).

Andy Waugh and Calum Mackinnon, the team behind Scottish restaurant and butchery company Mac & Wild, have announced they are to launch what they say will be the biggest single food and beverage site in Scotland, inside the shiny new Edinburgh St James development. Bonnie and Wild will cover over 16,000 sq ft, and will feature eight restaurant brands alongside a high-end retail offering.

Meanwhile, elsewhere in the Scottish capital, The Little Chartroom restaurant has opened a pop-up at the western end of the Portobello Prom, offering barbecue to take away. The menu, available from noon until six, Wednesday to Sunday, includes the likes of mussel popcorn, lamb flatbread with smoked aubergine and tomato anchovy sauce and an ox cheek pastrami bun with black garlic BBQ sauce. The Little Chartoom itself, over on Albert Place, has just reopened (thelittlechartroom.com).

Email Jay at jay.rayner@observer.co.uk or follow him on Twitter @jayrayner1